Re: [PATCHv1 dont apply] RFC: kvm eoi PV using shared memory

Avi Kivity
2012-04-17T09:24:43Z

On 04/16/2012 03:18 PM, Michael S. Tsirkin wrote:
> On Mon, Apr 16, 2012 at 02:24:46PM +0300, Gleb Natapov wrote:
> > On Mon, Apr 16, 2012 at 02:09:20PM +0300, Michael S. Tsirkin wrote:
> > > Thanks very much for the review. I'll address the comments.
> > > Some questions on your comments below.
> > >
> > > On Mon, Apr 16, 2012 at 01:08:07PM +0300, Gleb Natapov wrote:
> > > > > @@ -37,6 +38,8 @@
> > > > > #define MSR_KVM_SYSTEM_TIME_NEW 0x4b564d01
> > > > > #define MSR_KVM_ASYNC_PF_EN 0x4b564d02
> > > > > #define MSR_KVM_STEAL_TIME 0x4b564d03
> > > > > +#define MSR_KVM_EOI_EN 0x4b564d04
> > > > > +#define MSR_KVM_EOI_DISABLED 0x0L
> > > > This is valid gpa. Follow others MSR example i.e align the address to,
> > > > lets say dword, and use lsb as enable bit.
> > >
> > > We only need a single byte, since this is per-CPU -
> > > it's better to save the memory, so no alignment is required.
> > > An explicit disable msr would also address this, right?
> > >
> > We do not have shortage of memory.
> > Better make all MSRs works the same
> > way.
>
> I agree it's nice to have EOI and ASYNC_PF look similar
> but wasting memory is also bad. I'll ponder this some more.

Wasting three bytes?

> > BTW have you added new MSR to msrs_to_save array? I forgot to
> > checked.
>
> I didn't yet. Trying to understand how will that affect
> cross-version migration - any input?

It will just work.

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